From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932260AbbHCVyY (ORCPT ); Mon, 3 Aug 2015 17:54:24 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:57277 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753102AbbHCVyX (ORCPT ); Mon, 3 Aug 2015 17:54:23 -0400 Date: Mon, 3 Aug 2015 23:54:17 +0200 From: Peter Zijlstra To: Jiri Olsa Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Ingo Molnar , dong.su@ericsson.com, Vivek Goyal , Haren Myneni , Don Zickus Subject: Re: [RFC] perf: Clear MSRs on kexec Message-ID: <20150803215417.GG25159@twins.programming.kicks-ass.net> References: <20150803213228.GC14481@krava.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150803213228.GC14481@krava.redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 03, 2015 at 11:32:28PM +0200, Jiri Olsa wrote: > hi, > I'm getting following message on the kdump kernel start > > Broken BIOS detected, complain to your hardware vendor.\ > [Firmware Bug]: the BIOS has corrupted hw-PMU resources (MSR 38d is b0) > > it seems to be caused by NMI watchdog being configured > and fixed counter values stays in MSRs, which triggers > warning in check_hw_exists and disables perf support > in kdump kernel.. which probably does not hurt ;-) > > zeroing MSRs during kdump shutdown seems to work (attached) > but I'm not sure thats correct place for kdump perf callback Right, but why bother? All that kernel needs to do is write a memory dump to someplace and reboot, right? The less you do, the less can go wrong.